Method of manufacturing watertight electric fuses



N. SCHMITT Jan. 11', 1927.

"METHOD OF MANUFACTURING WATERTIGHT ELECTRIC FUSES Filed July 26. 1926Fig.3

Patented Jan.'11,1 927.

UNITED STATE-S uh h nrcomps sonm'r'r, or mnnnnnossmr'z, qnnmfir. v t

amnion or mumc'runme Application and miss, 1926, Serial up.

In blasting operations .it frequently occurs that the 7 have to becarried out in wet rock or comp etely under water. Hence it is necessarythat the electric fuses used shall 5 be made perfectly watertight, sothat they shall not become uselessthrough the action of the water. Themethods adopted hitherto with this object in view consist mainliyiigthis, that the caps of the fuses are embe either directly'm thedetonator or m a casing, into which the detonator is then cemented. As,however, all cementing materials more particularly the sulphur usuallyused for this purpose, contract when they solidify and the water wouldpenetrate through the which the priming composition is attached.

In a construction of this kind the wiresare bound to become loose whenhandled, thus rendering the 'acking inell'ective. 7

It has also lieen p oposed to cement the fuse into a cast casing whichis divided by a partition into two separate spaces, one of avhichreceives the incandescent wire and priming composition and the other-thedetonator. The carrying out of this idea is rendered difiicult'hy thecomplicated form of the casing, the manufacture of which is fairlyexpensive. But even in this construction water is not prevented frompenetrating to the primary composition, which fails to act when wet.

' By pressing delay compositions into the fuse casing the fuseisrendered watertight on the side facing the detonator. On the'other'side, however, is the cement for fixing the fuse wires into thiscasing as in fuses of the usual' kind which does not form a tightclosure as already explained above. The present invention has for itsobject to re der both. the detonator and the primarfccmposition tightagainst the penetrawarnnrren'r rane'rmc seats:

125,019 and in Germany mm yiia, 1921s.

ti on of moisture without any casingin the simplest mannerfbythefollowing method. 7

In the accom anymgdrawmg:

Figures 1 an 2 are longitudinal sectional.

and side views respectively of the fuse. 1

Figure 3 is an elevation ofthe fuse fitted.

with a detonator. 4

- Figures 4, 5 and dareelevations of modifications of the invention.

The fuse head of electric mine fuses are embedded in 'some suitablematerial, as

shown in section in Fig. 1, and in elevation in Fig. 2, a being the fusehead, I; the leadin'g-in wires and a the embedding material. Theembedding material may consist of resin, wax, paraflin, asphalt and thelike or of mixtures of these materials or of other suitable materials,which, however, must have the requisite strength and toughness and beeasily fused. 1 Y

When a fuse embedded in material of this kind is to be fitted with thedetonator d (fig. 3), the latter is inserted in the hole in t e metalplate 6 which has been heated by steam or hot water, so as to rest onthesupport f. The fuse-head (Fig. '2) is then inserted in the detonator.The embedded material on the fuse head has a-conical shapev and theexternal dimensions are such that the lower end will fit tightly in thedetonator. Through the detonator beingheated the surface of the embeddedmaterial will be melted, so that it canbe forced easi-- 1y down intothedetonator till the shoulder a. rests against the latter. This will bringabout such an intimate and permanentIcoii-a; =nect1on between the fusehead and the detona tor that water cannot possibly penetrate.

The finished fuse is imnie'diatelypushed out of the hot plate by raisingthe plunger f and is ready 7 for transport and use. Fig. 4 shows thecomplete fuse which may be left mentally afi'ected. T For fuses whichwithout detonators a modified form shall now he described. In Fig. 5 afuse is shown embedded in the manner described, which has a taperedextension 7:. at its lower end. If a fuse head of this kind be immersedin melted embedding material up to the shoulder, a portion of thematerial will adfor weeks under water without being-detrL are to betransportedhere toit, giving it the shape shown. at k in Fi 6. By thismethod the fuse head descri ed is not only protected against damage, butalso against being affected by water, to such an extent that the fusehead may lie in water for weeks without being detriin'entally afi'ected,even without the detonator, In addition to this the resent methodreliders the use of paper and brass casin superfluous, as detonators maybe placed on the fuse heads at the place where they are to be used, whenthey'wiil form a firm connection, owing to the conical shape of thehead.

' What I claim is: y

1. A method of manufacturing watertight electric fuses, consisting inproviding the fuse head'with aconical covering of an,

easily fusedmaterial, externally heating a detonator and inserting thesaid fuse head therein, whereby the two' are'oonnected together secureland in a watertight manner, as set forth. v

2. A method of manufacturing watertight electric fuses, consisting ,inproviding the fuse head with a tapered extension, immersing the'saidfuse head in'molten easily fused material, externally heating adetonator and inserting the said fuseheadtherein, whereby the two areconnected together securely and in a watertight manner, as "set. forth.

In testimony whereof l havesigned my name to this specification.

